The overall objective of this project is to analyze basic developmental processes in higher animals. Our particular goals are first, to understand the mechanisms whereby spatial patterns of differentiation are controlled during normal development and after injury--the processes of pattern formulation and pattern regulation--and second, to understand the processes which initiate and maintain states of determination, the developmental commitments which are made by cells and transmitted to their mitotic progeny. We are making extensive use of Drosophila in these investigations because of our conviction that the ultimate resolution of these problems at a molecular level will require the use of genetic mutations and genetic techniques which are available only in this organism. We are also using amphibians, because these are the vertebrates in which the processes of pattern regulation can most effectively be studied.